Exposure to highly estrogenic substances can disrupt reproduction and increase cancer risk, as well as influence bone metabolism and cardiovascular health. Chemicals that are weakly estrogenic are widespread in the environment, including several pesticides. Health effects of these environmental estrogens are not known. This project is designed to determine whether a test-case exposure to environmental estrogens, i.e., exposure to dietary soybeans (rich in plant estrogens)has the expected estrogenic effects. The experimental study compares women who were randomized to a soy-diet group with women who ate normally. We are looking for changes in LH, FSH, sex hormone binding globulin, apolipoprotein A-I, and vaginal smear cytology. If plant estrogens are found to act estrogenically in postmenopausal women, their effects on health outcomes such osteoporosis merit study. If not, the antiestrogenic effects of these compounds should be investigated.